Polyhydroxy polyurethane resins, which make use of carbon dioxide as a raw material, are known for some time as reported in Non-patent Documents 1 and 2. Under the current situation, however, the development of their applications has not moved ahead, because the above-described, conventionally-known resins are evidently inferior in characteristics to polyurethane-based resins as conventional, fossil-based high-molecular compounds (fossil-based plastics) (see Patent Documents 1 and 2).
However, the global warming phenomenon which can be considered to be attributable to the ever-increasing emission of carbon dioxide has become a worldwide problem in recent years, and a reduction in carbon dioxide emissions has arisen as a critical issue for the entire world so that there is an outstanding desire for a technology that makes it possible to use carbon dioxide as a production raw material. The change to renewable resources such as biomass and methane has also become a worldwide trend from the viewpoint of the problem of exhaustible fossil resources (petroleum).
Under such a background as described above, polyhydroxy polyurethane resins are drawing a fresh look again. Described specifically, carbon dioxide which is a raw material for these resins is a readily-available and sustainable carbon resource, and moreover, plastics that make use of carbon dioxide as a replacement for fossil resources can be considered to be an effective means for resolving problems such as the above-described warming and resource depletion.
It is, therefore, very preferable from the foregoing situation to realize the above-described replacement to polyhydroxy polyurethane resins, which can use carbon dioxide as a production raw material, in various applications where polyurethane-based resins as conventional fossil-based high-molecular compounds (fossil-based plastics) are used. Nonetheless, the conventional polyhydroxy polyurethane resins are inferior in characteristics to the fossil-based plastics as mentioned above. To spur the development of their applications, it is, therefore, essential to take into full consideration the circumstances in the respective applications and the performances suited for them and to develop resins capable of meeting these issues or requirements. A description will hereinafter be made about the conventional technologies in the respective applications.
(Thermal Recoding Media)
Conventionally-known thermal recording media include thermal fusion transfer recording media and thermal sublimation transfer recording media. In each thermal fusion transfer recording medium, a thermal recording layer (ink layer) is formed with a dye or pigment carried in a binder resin or the like on one side of a base sheet such as a polyester film, and from the back side of the base sheet, heat is applied in a pattern to transfer the ink layer onto a receiving medium. In each thermal sublimation transfer recording medium, on the other hand, a heat sublimation dye is used as a dye, and the dye alone is allowed to sublime such that it is likewise transferred onto a receiving medium.
These methods both employ the principle that thermal energy is applied by a thermal head from the back side of a base sheet, and therefore, the back side of the base sheet of a thermal recording medium to be used is required to have sufficient lubricity, separability, non-tackiness and the like with respect to the thermal head and the thermal head is also required not to stick to the back side (sticking phenomenon). Accordingly, there has been proposed, for example, a technology that forms a back side layer of a silicone resin, melamine resin, phenol resin, polyimide resin, modified cellulose resin or a mixture thereof on the back side of a base material sheet in a thermal recording medium (see Patent Document 3).
To form a heat-resistant protective layer on the above-described thermal recording medium with a view to providing its back side with heat resistance, attempts have been made, for example, to use various crosslinking agents in the above-described resins to thermally crosslink them or to add inorganic fillers, fluorinated resin powders or the like to these resins. These attempts can provide heat resistance, but are insufficient as measures for improving the lubricity and non-tackiness to a thermal head. Only the silicone resin out of the above-described resins is equipped with lubricity and non-tackiness, but this resin involves another problem in that damage is given to the base sheet, which is generally a thin film of from 2 to 5 μm thickness, in a heating step conducted to completely crosslink the resin. When the thermal recording medium is incompletely crosslinked to protect the base sheet from damage, on the other hand, the winding of the thermal recording medium into a roll form allows an unreacted, low-molecular silicone in the heat-resistant protective layer, which is formed on the back side of the base sheet, to migrate into the ink layer located in contact with the surface of the heat-resistant protective layer. As a result, a problem arises such that an image formed with such a thermal recording medium is unclear.
It is also known to use a silicone-acrylic graft or block copolymer in the heat-resistant protective layer. When a thermal recording medium is produced by this method, however, the heat resistance can be improved a little but the film-forming property of the acrylic component is insufficient so that the heat-resistant protective layer may separate from the base material. Moreover, this method is accompanied by a drawback that the heat-resistant protective layer is prone to abrasion and worn-out fragments of the protective layer deposit on a thermal head, thereby inducing new problems such as poor traveling and poor printing of the thermal recording medium and a reduced service life of the thermal head.
The present inventors studied on methods for solving these various problems, and proposed that the use of various silicone polyurethane copolymer resins makes it possible to obtain thermal recording media having a heat-resistant protective layer equipped with heat resistance, slidability, non-tackiness and the like in combination (see Patent Documents 4 to 6). These proposals were, however, not studied from the viewpoint of the preservation of the global environment, which has become a worldwide issue in recent years. It is, therefore, desired to review these technologies from such a new viewpoint.
(Imitation Leathers)
Conventionally, imitation leathers have been used in pouches, bags, shoes, furniture, clothing, vehicle interior trim materials, electric appliances, and the like. As resins for these imitation leathers, polyurethane-based resins are widely used. The term “imitation leather” is a generic term for leather-like products manufactured resembling natural leathers. In general, imitation leathers can be roughly divided into artificial leathers, synthetic leathers, and vinyl chloride leathers.
Artificial leathers have a structure closest to that of natural leathers among imitation leathers, and use a non-woven fabric as a base fabric. As a process for the production of a general artificial leather, there is a process to be described hereinafter. After a nonwoven fabric is first impregnated with a solution of a polyurethane-based resin in dimethylformamide (hereinafter, DMF), the polyurethane-based resin is solidified and dried into a porous form by wet-process film formation (submerged solidification). Subsequently, its surface is further coated with a polyurethane-based resin or provided with a laminated layer of the polyurethane-based resin to present a smooth tone, or its surface is ground to raise fibers such that a suede tone is presented.
On the other hand, synthetic leathers use, as a base fabric, a fabric such as a woven fabric or raised blanket, and in general, are roughly divided into dry-process synthetic leathers and wet-process synthetic leathers. For the production of a dry-process synthetic leather, there are two processes, one being to coat a polyurethane-based resin directly on a base fabric and to dry it, and the other to coat a polyurethane-based resin on a sheet of release paper, to dry the polyurethane-based resin into a film, and then to bond the film and a base fabric together with an adhesive. On the other hand, a wet-process synthetic leather can be produced by impregnating or coating a base fabric with the above-mentioned solution of the polyurethane-based resin in DMF and then subjecting the polyurethane-based resin to submerged solidification and drying to form a porous layer. Further, the surface of the synthetic leather obtained by the dry process or wet process as described above is coated with a polyurethane-based resin or provided with a laminated layer of the polyurethane-based resin to present a smooth tone, or the surface is ground to raise fibers such that a suede tone is presented.
There is an increasing consciousness towards the preservation of the global environment in recent years. The change to renewable resources such as biomass and methane has become a worldwide trend from the viewpoint of the problem of exhaustible fossil resources (petroleum). Under such a background, more and more makers are also positively working on environmental measures in the field of imitation leather products in recent years, resulting in a move toward forming imitation leather products by using materials excellent in environmental preservation properties. A great deal of research is hence under way, for example, to reduce VOC (volatile organic compound) emissions as much as possible by using as polyurethane-based resin those which are dispersible or emulsifiable in water-based media in place of organic solvents or to use plant-derived raw materials from the viewpoint of carbon neutral (Patent Documents 7 to 9). However, the resulting imitation leather products are still different in performance compared with the conventional products, and therefore, are considered to have problems for practical applications. Moreover, these approaches are still insufficient in respect to the solution of new environmental problems such as the reduction of carbon dioxide emissions, which has become a critical worldwide issue.
(Skin Materials Made of Thermoplastic Polyolefin Resins)
The recycling of vehicle interior trim materials (instrument panels, door trims, etc.) and home electric appliance components and parts is strongly desired to decrease waste materials as much as possible after use in view of the garbage-related problems and environment-related problems in recent years. From this viewpoint, thermoplastic polyolefins, for example, polypropylene (PP), ABS resin, AS resin, polyolefin-based thermoplastic elastomers (TPO) and the like are used as skin materials for vehicle interior trim materials and home electric appliance components and parts in recent years. However, these thermoplastic polyolefins are inferior in surface adhesiveness, scratch resistance, abrasion resistance and chemical resistance in comparison with vinyl chloride resin and the like which have been conventionally used, and therefore, are required to apply coatings in order to improve them in these properties. It is also necessary to provide artistry for giving a high-grade appearance, and especially in the case of car interior trim materials, to consider not only artistry but also an attention to anti-glare properties for drivers and like properties. It is, therefore, a current practice to apply various coatings to thermoplastic polyolefin base materials such that top coat layers are formed to impart a function to their surfaces for the provision of still better skin materials.
In the coating formulations to be employed as described above, the below-described resins and the like are used, and a variety of studies have been made on such resins. Proposals have been made including, for example, a method that employs a coating formulation making use of a chlorinated polypropylene-modified acrylic resin, which has good adhesiveness to polyolefin-based resins such as PP resin and TPO resin, as a binder and containing a matting agent such as an inorganic extender pigment (silica or talc) or acrylic resin particles added thereto and a method that applies a chlorinated polypropylene-based primer and then applies on the primer a coating formulation containing a polyester resin or polyurethane resin.
There is an increasing consciousness towards the preservation of the global environment in recent years. The change to renewable resources such as biomass and methane has become a worldwide trend from the viewpoint of the problem of exhaustible fossil resources (petroleum). Under such a situation, more and more makers are also positively working on environmental measures in the field of the above-descried skin materials made of thermoplastic polyolefin resins in recent years, resulting in a move toward forming such products by using materials excellent in environmental preservation properties. A great deal of research is hence under way, for example, to avoid choosing specific solvents (toluene and the like) from organic solvents for use in the above-described coating formulations or to use water-based resins instead of organic solvents for reducing VOC (volatile organic compound) emissions as much as possible (Patent Documents 10 to 12). However, these approaches are also still insufficient in respect to the solution of new environmental problems such as the reduction of carbon dioxide emissions, which has become a critical worldwide issue.
(Weather Strip Materials)
As materials for forming weather strips such as glass runs, door weather strips, body side weather strips, inside seals and outside seals in cars and buildings, high-molecular elastomer materials such as chloroprene rubber, styrene-butadiene rubber, nitrile rubber and EPDM rubber have been used conventionally. It is a common practice to form surface treatment layers on the surfaces of these weather strips by a method such as coating or impregnation such that performance such as lubricity, abrasion resistance, mold release properties, heat resistance, water resistance and weatherability can be imparted.
As materials for forming such surface treatment layers, a variety of coating formulations have been proposed including one containing a thermosetting polyurethane resin and a silicone oil added thereto (see Patent Document 13), one containing a thermosetting polyurethane resin and an organopolysiloxane added thereto (see Patent Document 14), and one composed of a urethane prepolymer, a silicone oil, hydrophobic silica and a polyisocyanate (see Patent Document 15).
On the other hand, there is an increasing consciousness towards the preservation of the global environment in recent years. The change to renewable resources such as biomass and methane has become a worldwide trend from the viewpoint of the problem of exhaustible fossil resources (petroleum). Under such a situation, more and more makers are positively working on environmental measures, resulting in a move toward forming weather strips by using materials excellent in environmental preservation properties. A great deal of research is hence under way, for example, to avoid choosing specific solvents (toluene and the like) from organic solvents for use in the above-described coating formulations or to use water-based resins instead of organic solvents for reducing VOC (volatile organic compound) emissions as much as possible (see Patent Document 16). However, these approaches are also still insufficient in respect to the solution of new environmental problems such as the reduction of carbon dioxide emissions, which has become a critical worldwide issue.